During vehicle driving (including vehicle stopping), an engine commonly runs in an idling condition when there is no need to produce driving power (e.g., when an accelerator pedal is released during vehicle stopping or vehicle decelerating). However, this may result in not only reducing fuel economy performance of the vehicle but also unnecessarily increasing carbon dioxide emission which could be a cause of global warming, since the fuel might be consumed wastefully.
Thereupon, many kinds of so-called idling stop engines have been proposed recently. The idling stop engine might stop automatically by stopping a fuel supply into the engine when there is no need to produce the driving power, and then restart automatically by restarting the fuel supply into the engine when there happens to be need to produce the driving power again.
For example, Japanese Unexamined Patent Application Publication No. 2004-108327 discloses an idling stop engine, which restarts the fuel supply when an engine rotating speed reaches a predetermined rotating speed due to a motor (driving motor) for rotating the engine in the case of restarting the engine after automatically stopping the engine. However, even if the engine rotating speed reaches the predetermined rotating speed, the vehicle might not necessarily be in a state requiring a restart of the fuel supply (e.g., in a state requiring vehicle starting or vehicle accelerating). Accordingly, in these known idling stop engines, the fuel might be supplied too early when there is still no need to supply the fuel into the engine, which disadvantageously might not improve the fuel economy performance (which was expected to be improved by automatically stopping the engine).
This invention is made so as to address the above problem. Therefore, the purpose of the invention is to provide an engine control method and an engine control device which could reduce or prevent the unnecessary fuel consumption by restarting the engine at a suitable timing where the fuel supply should be restarted after automatically stopping the engine.